A communication system can be seen as a facility that enables communication sessions between two or more entities such as fixed or mobile communication devices, base stations, servers and/or other communication nodes. A communication system and compatible communicating entities typically operate in accordance with a given standard or specification which sets out what the various entities associated with the system are permitted to do and how that should be achieved. For example, the standards, specifications and related protocols can define the manner how communication devices can access the communication system and how various aspects of communication shall be implemented between communicating devices. A communication can be carried on wired or wireless carriers. In a wireless communication system at least a part of the communication between at least two stations occurs over a wireless link.
Examples of wireless systems include public land mobile networks (PLMN) such as cellular networks, satellite based communication systems and different wireless local networks, for example wireless local area networks (WLAN). A wireless system can be divided into cells, and hence these are often referred to as cellular systems. A cell is provided by a base station. Cells can have different shapes and sizes. A cell can also be divided into sectors. Regardless of the shape and size of the cell providing access for a user, and whether the access is provided via a sector of a cell or a cell, such area can be called radio service area or access area. Neighbouring radio service areas typically overlap, and thus a communication in an area can listen to more than one base station.
A user can access the communication system by means of an appropriate communication device. A communication device of a user is often referred to as user equipment (UE) or terminal. A communication device is provided with an appropriate signal receiving and transmitting arrangement for enabling communications with other parties. Typically a communication device is used for enabling receiving and transmission of communications such as speech and data. In wireless systems a communication device provides a transceiver station that can communicate with another communication device such as e.g. a base station of an access network and/or another user equipment. The communication device may access a carrier provided by a station, for example a base station, and transmit and/or receive communications on the carrier.
An example of communication systems attempting to satisfy the increased demands for capacity is an architecture that is being standardized by the 3rd Generation Partnership Project (3GPP). This system is often referred to as the long-term evolution (LTE) of the Universal Mobile Telecommunications System (UMTS) radio-access technology. The LTE aims to achieve various improvements, for example reduced latency, higher user data rates, improved system capacity and coverage, reduced cost for the operator and so on. A further development of the LTE is often referred to as LTE-Advanced. The various development stages of the 3GPP LTE specifications are referred to as releases.
In LTE-Advanced the network nodes can be wide area network nodes such as a macro eNodeB (eNB) which may, for example, provide coverage for an entire cell. Alternatively in LTE-Advanced, network nodes can be small area network nodes such as pico eNodeBs (pico-eNB). Small area network nodes may be configured to support local offload and may support any UE or UEs belonging to a closed subscriber group (CSG) or an open subscriber group (OSG). Pico eNBs can, for example, be configured to extend the range of a cell. In some instances a combination of wide area network nodes and small area network nodes can be deployed using the same frequency carriers (e.g. co-channel deployment) to provide overlapping cell layers.
One aspect of LTE-Advanced is that a Multimedia Broadcast/Multicast Service (MBMS) for a Universal Mobile Telecommunications System (UMTS) can be provided. The MBMS uses broadcast or multicast message distribution instead of several point-to-point links for communicating to several end user equipments.
A UE that operates in a UMTS or LTE network can obtain communication services using procedures according to a standard defined by the 3GPP. The standard specifies, for both of these networks, radio system parameters, data transfer procedures, network protocols, control messages and bearer traffic exchange to take place over the air interface. The MBMS can allow efficient session management by enabling service data packets to be transferred in an efficient way to multiple UEs within these networks. For this purpose, a message can be transmitted from a core network node to several node Bs (nBs). Each NB can then send a unidirectional point-to-multipoint (PtM) transmission to UEs so that a UE in an idle or active mode receives network service data.
In a multicarrier environment an MBMS broadcast/multicast may be configured for a certain cell layer to provide efficient radio resource usage for the MBMS broadcast/multicast. At certain locations in a communications network there may be multiple cell layers with different cell sizes provided by different base stations. Certain mobility management rules of the network may determine that UEs are handed over to smaller base stations providing smaller cell layers whereas other UEs are kept on macro cell layers. A problem can arise if the network does not know about the UE being able to receive MBMS broadcasts/multicasts. The network can hand the UE over to another cell layer which does not support MBMS broadcasts/multicasts which can disrupt MBMS reception for the user equipment.